This invention relates generally to a braked joint assembly for rotatable support of a grapple mechanism, a clam shell device or the like, and more particularly, to a braked joint assembly including a load carrying bushing or bearing arrangement and a separate frictional brake arrangement utilizing opposed outwardly tapered or conical frictional brake elements for improved operability and cost aspects.
Grapple mechanisms, clam shells, and the like, are commonly suspended from the free or distal ends of boom assemblies of skidders, construction machines, and the like, for carrying pulpwood, logs and other heavy loads. Typically the grapple mechanisms and other load carrying elements are suspended from the boom assembly using at least one pin joint to allow relative rotational or pivotal movement in at least one plane. Such pin joints typically include snubbers or brakes for resisting or dampening the rotational or pivotal movement to limit the possibility of damage to the machine and personnel. However, the known pin joints including snubbers or brakes have been found to suffer from various operational, maintenance and cost disadvantages.
Reference in this regard, Johnson U.S. Pat. No. 4,573,728 issued Mar. 4, 1986 which utilizes a snubbing apparatus with planar frictional elements which suffers from the operational disadvantage of requiring high compression of the assembly to provide adequate snubbing torque. Reference also McCallum U.S. Pat. No. 5,713,688 issued Feb. 3, 1998 which discloses a braked mechanical joint assembly utilizing tapered or frusto-conical sections which taper inwardly, that is, convergingly toward the center of the joint for bearing both load forces and braking torques, which has been found to be unable to withstand operational loads under heavier loading conditions.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, an improved braked or snubbed joint assembly for supporting a grapple mechanism, clam shell or like device, is disclosed. The present braked or snubbed joint assembly includes a first member including an element defining an elongate cylindrical bore therethrough having a central axis, and first and second outwardly tapered or conical convex axial end faces extending around the bore. The present joint assembly includes a second member having first and second arms defining a space therebetween receiving the first member, the first arm including an element disposed in the space having a tapered concave axial end face located in spaced opposed relation to the first tapered or conical convex axial end face of the first member and the second arm including an element disposed in the space having a tapered concave axial end face located in opposed relation to the second tapered or conical convex axial end face, the arms having holes axially aligned with the bore of the first member. The present joint assembly includes a pin extending through the axially aligned holes and the bore rotatably joining the first member and the second member. Frictional brake elements are disposed respectively between the opposed tapered axial end faces for frictionally resisting or braking relative rotation of the first and second members.
Advantages of the braked or snubbed joint assembly of the present invention includes the separate performance of the load bearing and braking or snubbing functions by the elements defining the cylindrical bore of the first member, and the frictional elements, respectively. The tapered shape of the axial end faces provides a wedging effect which enables high contact forces to be generated between the tapered end faces and the brake elements for improved braking or snubbing torque. Additionally, the outwardly tapered axial end surfaces of the first member enable the element defining the cylindrical bore to be relatively long so as to be capable of carrying heavy loads and to last longer. Still further, the outwardly tapered shape enables the frictional elements to have larger surface areas of engagement so as to provide improved braking or snubbing and better dissipation of heat generated by the frictional contact.